Overview: One of the long-term goals of the automotive manufacturers is to reduce fuel consumption and emissions of modern automotive vehicles powered by internal combustion engines (ICE) while increasing engine efficiency. One approach to reaching this goal is reducing the ICE displacement. However, smaller engines having reduced swept volume typically exhibit insufficient power and torque when operating with normal aspiration. This problem can be remedied by supercharging. It is well known in the art that ICE power output increases with increased weight of air ingested into engine cylinders and available for combustion. Weight of air ingested into engine cylinders can be increased by either 1) increasing the pressure of intake air beyond what can be accomplished by natural aspiration or by 2) cooling the intake air or 3) by a combination of 1) and 2). Therefore, a supercharged ICE receives combustion air with higher density than a normally aspirated ICE. As a result, supercharging allows generating increased power from an engine of a given displacement or, generating a given power output from an engine of smaller size, weight, cost, and emissions.
Superchargers: Supercharges have long been utilized for boosting the power output of ICE's of each spark ignition and compression ignition (diesel) type. Superchargers can be generally classified according to their source of motive power as engine-driven and exhaust gas turbine-driven. The latter are also know as turbochargers. Modern engine-driven supercharger is a positive displacement pump (e.g., Roots blower, vane compressor, or a screw compressor) mechanically coupled to the engine. One limitation of engine-driven superchargers is the low volumetric output at low engine speeds which translates to insufficient torque and poor vehicle acceleration. While this may be remedied by a variable speed drive, the penalty is an increase in complexity and cost. In addition, engine-driven supercharger requires significant ICE power to operate and this power must be supplied at the least opportune moment, namely during high demand on ICE output. As a result, ICE output power available for propulsion is reduced by the amount required to operate the supercharger. Finally, an engine-driven supercharger must be engaged in a controlled manner to avoid a sudden surge in ICE intake pressure and the consequential sudden surge in output torque. This often requires a complex control system.
An exhaust gas turbocharger typically includes a turbine and a centrifugal compressor on a common shaft. The turbine is rotated by exhaust gases from the engine and spins the compressor. The compressor receives intake air, compresses it, and supplies it to ICE combustion chamber(s). Turbochargers provide the advantages of relatively smooth transitions from natural aspiration to supercharged operation while utilizing some of the residual energy of hot exhaust gas, which would otherwise be largely wasted. One drawback of a turbocharged engine is a slow response time known as the “turbo-lag” which is caused by the low pressure and low quantity of exhaust gases at low engine speeds. Consequently, a standard exhaust gas turbocharger is only effective above about 1800 rpm of the ICE. This means that a small displacement ICE equipped with a turbocharger is susceptible to insufficient torque at low engine speeds. Quick acceleration of the turbocharger to normal operating speed is further impeded by the turbocharger rotational inertia. These problems may be corrected in-part by the use of a variable nozzle turbine, which alters the cross-sectional area through which the exhaust gas flows in accordance with engine speed. While this approach recovers some of the intake air pressure lost to low ICE speed, it adds complexity and cost, and reduces reliability.
Recently, an electrically-assisted turbocharger (also known as the “e-turbo”) has been proposed to remedy the turbo lag. Since the e-turbo makes supercharging independent of engine speed, it promises to virtually eliminate the turbo lag. Generally, in the e-turbo, electric power drawn from vehicle electric system (e.g., battery) is provided to an electric motor which spins a turbo-compressor. There are two different types of e-turbo known in the automotive industry. The first type of e-turbo is formed by directly coupling an electric motor to the shaft of a conventional exhaust turbocharger, as disclosed, for example, by Kawamura in U.S. Pat. No. 4,958,497. A drawback of this approach is that during acceleration of the e-turbo to operational speed the electric motor has to overcome the compound inertia of both the turbo-compressor and the exhaust turbine while additionally being exposed to very high temperatures. The second type of e-turbo is formed by coupling an electric motor to a turbo-compressor, as disclosed, for example, by Woolenberger et al., in U.S. Pat. No. 6,079,211. This type of an e-turbo can be used in series or in parallel with a conventional turbocharger to reduce turbocharging lag and to increase torque at low ICE speeds, such as disclosed, for example, by Hoecker et al., in U.S. Pat. No. 6,889,503. However, both e-turbo approaches face the challenge of attaining the extremely fast startup and acceleration to reach operating speeds of 50,000 to 70,000 revolutions per minute (rpm) in less than one second. To meet this challenge may require ultrahigh power electronics and electric power source combined with sophisticated computer control. In particular, according to an article authored by Thomas Kattwinkel et al. entitled “Mechatronic Solution for Electronic Turbocharger” SAE paper number 2003-01-0712 published by the Society of Automotive Engineers, Inc., Warrendale, Pa., the e-turbo electric demand cannot be satisfactorily met with a standard 12 volt automotive battery system unless additional intermediate electric energy storage (e.g., super-capacitors) is provided.
Supercharging with Compressed Air from Storage Tank: Another approach to supercharging ICE during period of increased power demand is to provide the ICE with compressed air from a storage tank in lieu of normal aspiration as disclosed, for example, by Weich et al. in U.S. Pat. No. 3,673,796. In this approach, a near instantaneous supercharger response to power demand may be obtained. One disadvantage of this approach is that the potential energy in compressed air is largely wasted because the air is vented from the storage tank at high pressure to ICE intake which is at a much lower pressure. This disadvantage may be overcome by employing an ejector operated by compressed air to pump ambient air into ICE intake such disclosed by the Applicant in U.S. Pat. No. 7,076,952. As compressed air flows through a driving nozzle of the ejector, it forms as high-velocity air stream which entrains some of the surrounding air and forces it into ICE intake thereby increasing ICE intake air pressure. Ejector thus converts potential energy of compressed air in the storage tank into kinetic energy of the nozzle flow which is then converted back into potential energy of pressurized intake air. Because ICE intake air is a mixture of air flowing through the ejector driving nozzle and the air pumped by the nozzle flow, the amount of compressed air required to operate an ejector supercharger is considerably smaller than if compressed air was merely vented from a storage tank into ICE intake.
Ejector pumps are widely used in industry for pumping liquids and gases, see for example, R. H. Perry and C. H. Chilton, “Chemical Engineer's Handbook,” 5th edition, Chapter 6, Section “Ejectors,” pages 6-29 to 6-32, published by McGraw-Hill Book Company, New York, N.Y., 1973, and G. L. Weissler and R. W. Carlson (editors), “Vacuum Physics and Technology,” Chapter 4.3.5: Ejectors, pages 136 to 138, published by Academic Press, New York, N.Y., 1979. One key advantage of ejector pumps is that they are mechanically simple as they have no pistons, rotors, or other moving components. Ejector based supercharger may provide a nearly instantaneous response to power demand and it also offers smooth transition from natural ICE aspiration to supercharged condition. Furthermore, air compression by ejectors is nearly isothermal and, therefore, an intercooler commonly used with engine driven superchargers and exhaust gas turbochargers may not be required. Ejectors which produce output flow at above ambient atmospheric pressure are also known as thermo-compressors. Superchargers employing ejectors with a straight or converging nozzle produce only subsonic or sonic flow and, therefore have only a very limited compression capability. A considerably higher compression can be attained by an ejector-based supercharger having a supersonic nozzle flow.
Vortex Tube for Cooling of ICE Intake Flow: It has been already stated above that reduction of ICE charge temperature increases the charge density and thus increases ICE capacity to produce more power. In addition, reduced charge temperature is known to cut ICE emissions by decreasing charge pre-ignition also known as knocking. Vortex tube is a well known cooling device in the art of refrigeration. Traditional vortex tube comprises a slender tube having one end closed except for a small a central opening and the other end plugged except for an annular opening which may be adjusted in size for flow control, see FIG. 1. A stream of high-pressure air (or other suitable gas) is injected through an inlet port tangentially into the tube in the proximity of the central opening. Resulting vortex flow pattern inside the tube separates the input air stream into a relatively hot air stream which exits through the annular opening and a relatively cold air stream which exits through the central opening and the cold outlet port. Relative flow rates and temperatures of these two streams are typically adjustable by controlling the flow of the hot exhaust stream. See, for example, article entitled “The Vortex Tube as a Classic Thermodynamic Refrigeration Cycle,” by B. K. Ahlbom et al., published in Journal of Applied Physics, Volume 88, Number 6, pp. 3645-3653, Sep. 15, 2000. A variant of the traditional vortex tube suitable for generating only a cold output stream can be produced by entirely closing one of the tube ends combined with active cooling of the tube exterior surface such as shown in FIGS. 2A and 2B and disclosed, for example, by Zerr in U.S. Pat. No. 4,612,646. Suitable cooling may be provided by a cooling jacket which may envelop the tube exterior surface. Suitable coolants may be provided in liquid or gaseous form. The exterior surface of the tube can be further provided with surface extensions to facilitate improved heat transfer as disclosed, for example, by Tunkel et al. in U.S. Pat. No. 5,911,740. Vortex tube may also exhaust flow into pressures below atmospheric pressure as disclosed, for example, by B. R. Belostotskiy et al. in an article “Vortex-Flow Cooled Laser,” published in Soviet Journal of Optical Technology, volume 35, number 1, pp. 450-452, January-February 1968, and by Tunkel et al. in U.S. Pat. No. 5,561,982.
Lindberg et al. in U.S. Pat. No. 6,247,460 discloses an ICE having a vortex tube for cooling intake air. Lindbergh's vortex tube generates both cold and hot outputs with only the cold output supplied to ICE intake. All of the intake air flows through the vortex tube at all times. When used on a supercharged ICE, the intake air pressure drop inside the vortex tube robs the ICE of the pressure boost provided by the supercharger and wastes much of the supercharger output into vortex tube hot flow. Similarly, when used on a naturally aspirated ICE, the vortex tube impedes intake air flow thereby reducing the intake air pressure. In both cases the benefit of providing a cooler air to the ICE is accomplished at the expense of reducing the intake air pressure. In particular, data of some vortex tube manufacturers suggests that the pressure ratio between vortex tube inlet port and its cold outlet port should be at least 1.4. Since cooling of the intake air and reducing its pressure have opposite effects on air density, the net benefit of Lindberg's apparatus, if any, is rather limited.
Holman et al. in the U.S. Pat. No. 6,895,752 discloses a turbocharged ICE with an exhaust gas recirculation (EGR) system wherein ICE exhaust is directed to a vortex tube to generate a cooler flow and a hotter flow. The cooler flow is directed to ICE intake to recirculate part of the exhaust gas while the hot flow is exhausted from the ICE in a conventional manner.
In summary, prior art does not teach a supercharged ICE system that is effective during the conditions of high torque and low engine speed, has a fast response, is simple, economical, and can be retrofitted onto existing ICE, does not require exotic electric motors and power supply, avoids exposing electrical components to high temperatures, does not rob engine of power during high power demand, and reduces susceptibility to charge pre-ignition. Furthermore, the prior art does not teach an ICE where intake air is mixed with cold air from a vortex tube. Moreover, prior art does not teach an ICE supercharged by an ejector pump operated by a cold air generated by a vortex tube. It is against this background that the significant improvements and advancements of the present invention have taken place.